(a) Field of the Invention
The present invention relates to a thin film transistor substrate for a liquid crystal display and a manufacturing method thereof, in particular, to a thin film transistor substrate having buffer layers and a manufacturing method thereof
(b) Description of the Related Art
A thin film transistor liquid crystal display is a widely used display and is manufactured by using several photo masks.
A conventional substrate for liquid crystal display is described with reference to FIG. 1.
FIG. 1 shows a cross sectional view of a conventional thin film transistor for a liquid crystal display shown in the specification of Korean Patent Application No. 95-52714. A gate pattern including a gate electrode 33a is formed on a substrate 31 and an anodic oxidation film 35 is formed on the gate pattern. A gate insulating film 37 is formed thereon and an active pattern 39 is formed on the gate insulating film 37 at the position corresponding to the gate electrode 33a. An indium-tin-oxide (ITO) is formed on the active pattern 39 and the gate insulating film 37 and divided into two portions 410 and 420 with respect to the gate electrode 33a. One of the portions is a source electrode and the other is a drain electrode. A passivation film 43 covers the source electrode, the drain electrode and the active pattern 39. The passivation film 43 has a contact hole exposing the portion 420, and the portion 420 contacts a data line 45 through the contact hole.
However, in this thin film transistor, contact resistance between the active pattern 39 and the ITO film 420 is large because the active pattern 39 directly contacts the ITO film 420. In addition, the portion of the data line 45 which plays a role of contact pad may not be protected because the data line 45 is formed over the ITO film 420.